Final answer:
The correct way to combine the sentences is 'The electricity was out, and we had no candles,' which demonstrates proper use of commas and conjunctions in sentence structure.
Step-by-step explanation:
The sentence provided by the student, "The electricity was out. We had no candles.", can be correctly combined using option c: "The electricity was out, and we had no candles." This option correctly joins two independent clauses with a comma followed by a coordinating conjunction (and), which agrees with conventional rules of grammar. Option a implies a causal relationship that is not present in the original sentence, and option b is a comma splice – two independent clauses incorrectly joined by a comma without a coordinating conjunction.
This topic falls under the broader category of grammar and punctuation, where understanding the correct use of commas and conjunctions is essential. Reviewing example sentences for correct punctuation helps clarify these rules. As seen in sentences like "Susan was sitting off in the corner; without a care in the world," which correctly use a semicolon when a coordinating conjunction is not present, and "Lawmakers recommended the bill be changed before the final vote," where the correct spelling of 'recommended' is used.